Aqueous Solutions Of NaNO3 Research Articles

Electrochemical behavior of silver single-crystal electrodes in 1 M NaNO3 solution in the absence and in the presence of decanethiol films

The surface properties of silver single-crystal faces (111) and (210) in 1 M NaNO3 aqueous solution in the absence and in the presence of monolayer n-decanethiol (DT) films are studied by the methods of cyclic voltammetry and electrochemical impedance using the meniscus contact technique. It is experimentally shown that, in the potential range from 0 to −0.5 V, the faradaic processes are absent and low currents are recorded on the unmodified silver surfaces. It is shown that the DT molecules, which are adsorbed on the nonoxidized surfaces of silver faces, spontaneously form (during 72 h) compact structurized films. The films are stable in the air and in the electrolyte solutions and totally block the surfaces of both faces. The impedance spectra, which were measured for each interface in a wide range of frequencies, are analyzed and interpreted. The measurements were performed by the use of the corresponding empirical equivalent circuits containing perfect and imperfect analogs of electrical circuits; complex nonlinear least squares (CNLS) regression method was applied for the calculations. The capacitance, ohmic resistance, and adsorbed monolayer thickness were estimated.

The measurement of growth rates in capillary jets

The growth of perturbations on a capillary jet issuing from a circular nozzle in the Rayleigh regime is experimentally investigated. Electrohydrodynamic sinusoidal stimulation is employed to this end, along with two independent methods to obtain growth rates of the linear regime with the best accuracy so far. The first method exploits the correlation between the stimulation voltage and the breakup time measured with the help of stroboscopic images of the jet. The second method is an analysis of the spatial evolution of perturbations through a local jet-shadow-width photometry, with careful avoidance of the initial transient and the final nonlinear stages. Experiments conducted with ink allow the application of both methods, as the liquid is opaque. They give consistent results, with very small statistical errors, with respect to the expected theoretical dispersion relation, once the dynamic surface tension is adjusted. The adjusted value is in accordance with an estimate made from drop-dynamics experiments also reported here. By dealing with a simpler liquid (aqueous solution of NaNO3), we are able to compare results from the first method against the theoretical predictions without adjustment of any parameter. The agreement is again excellent. Possible sources of systematic errors in this kind of measurements are identified and procedures for avoiding them are designed.

Application of Mixture Models to Solubility Calculations, Using Sodium Oxalate as an Example

The solubility of solids in nuclear waste impacts many separation processes including evaporator set-points, pressure drops in ion-exchange columns, as well as the washing and leaching of sludge. Scheffe and Cox type empirical mixture models have long been used to model crystal stability in nuclear waste glass melters, and this methodology has now started being employed to model solubility in aqueous nuclear wastes. The large amount of theory and data available for aqueous systems allows for the opportunity to evaluate mixture models for solubility calculations. In the present paper, it is shown that Scheffe type mixture models should be employed when the pure component is the standard state of interest whereas the Cox type mixture models should be employed when infinite dilution is the standard state. An example application is used to demonstrate that mixture models can be used to predict solubility, even across a phase boundary, when combined with the standard thermodynamic equations for the solubility product. The example employed is Na2C2O4 solubility in aqueous NaNO3 solutions, which can be thought of as a simplified high-level nuclear waste supernatant.

Selective Adsorption of Poly(ethylene oxide) onto a Charged Surface Mediated by Alkali Metal Ions

Using a surface force balance, we have measured normal and shear interactions between mica surfaces across pure water and across 0.1 M aqueous solutions of LiNO3, NaNO3, KNO3, and CsNO3, both prior to adding polymer and following addition of 1.5 x 10(-4) w/w poly(ethylene oxide) (PEO, Mw = 170 kD) and overnight incubation. Our results reveal that while the PEO adsorbs strongly from the KNO3 and CsNO3 solutions, unexpectedly it does not adsorb at all from the LiNO3 and NaNO3 salt solutions. We attribute this to the different nature of the hydration layers about the alkali metal ions: these favor liganding to the negatively charged mica surface of the etheric -O- group on the ethylene oxide monomer for the case of the more weakly hydrated K+ and Cs+, but not for the case of Na+ or Li+ with their more strongly bound water. A simple model relating the electrostatic energy changes occurring upon such liganding to the experimentally measured hydration energies of the different alkali metal ions supports this attribution.

Relationship between Swelling and the Electrohydrodynamic Properties of Functionalized Carboxymethyldextran Macromolecules

The electrostatic, hydrodynamic, and swelling properties of a well-defined, functionalized carboxymethyldextran (CMD) polysaccharide are investigated in aqueous NaNO3 solution over a broad ionic strength range. The impact of the polycarboxylate charge and molar mass of the CMD macromolecules on their electrohydrodynamic features is thoroughly examined by combined protolytic titration, dynamic light scattering, and electrokinetic analyses. Electrophoretic mobility data obtained for sufficiently high electrolyte concentrations reveal a typical soft particle behavior. Upon decrease of the ionic strength, mobilities strongly increase in magnitude while significant electrostatic swelling takes place, as reflected in a decrease in the diffusion coefficients. CMD entities undergo conformational transitions from compact random coil at large ionic strengths to swollen coil and possibly a wormlike structure at lower NaNO3 concentrations. The magnitude of the variations in size and mobility with electrolyte concentration strongly depends on the overall charge of the CMD entity as well as on its molar mass. These factors control the stiffness of the constituent polymer chains and thus the degree of macromolecular permeability ("softness"). Using the soft-diffuse interface formalism previously developed for the electrohydrodynamics of charged permeable macromolecules, a quantitative analysis of the electrophoretic mobility data is presented. The measured values of the diffusion coefficient and space charge density Gamma degrees, as evaluated independently from the modeling of potentiometric titration curves, are taken into account in a self-consistent manner. It is found that large CMD entities of low charge densities are the most permeable to flow penetration with a limited heterogeneous electrostatic stiffening of the chains, whereas small CMD entities of larger Gamma degrees significantly expand upon lowering the ionic strength, giving rise to a strong anisotropy for the spatial distribution of polymer chain density.

Enthalpies of Transfer of Amino Acids from Water to Aqueous Solutions of Alkali Metal Nitrates

Enthalpies of solution of glycine, l-alanine, and l-serine in water and aqueous solutions of LiNO3, NaNO3, and KNO3 were measured at 298.15 K. Enthalpies of transfer (ΔtrH) of amino acids from water to aqueous solutions of nitrate salts were derived. The effect of the ion type, concentration, and structure of amino acids on the magnitude of the transfer enthalpies are discussed in terms of the electrostatic interaction and the structural hydration interaction model.

Is There an Anionic Hofmeister Effect on Water Dynamics? Dielectric Spectroscopy of Aqueous Solutions of NaBr, NaI, NaNO3, NaClO4, and NaSCN

A systematic study of the dielectric relaxation spectra of aqueous solutions of NaBr, NaI, NaNO(3), NaClO(4), and NaSCN has been made over a wide range of frequencies (0.2 < or = nu/GHz < or = 89) and solute concentrations (0.05 < or = c/M < or = 1.5) at 25 degrees C. The spectra could be adequately described by a single Cole-Cole (CC) process, symmetrically broadened relative to that of pure water. However, similar quality fits were also obtained with a three-Debye-process (3D) model consisting of a small ion-pair contribution at lower frequencies and two solvent relaxations at higher frequencies. Assuming the ions to be solvent separated, the 3D model provided estimates of their association constants and their rate constants for formation and dissociation. The bulk water relaxation times obtained from both models showed almost no dependence on the nature of the anion. Nevertheless, there were subtle differences in the concentration dependences of the relaxation times which correlated with some, but not all, of the anion properties that are believed to be relevant for explaining the anionic Hofmeister series.

Photochemical Production and Release of Gaseous NO2 from Nitrate-Doped Water Ice

Temperature-programmed NO2 emissions from frozen aqueous NaNO3 solutions irradiated at 313 nm were monitored as function of nitrate concentration and heating rate, H, above -30 degrees C. Emissions increase nonmonotonically with temperature, displaying transitions suggestive of underlying metamorphic transformations. Thus, NO2 emissions surge at ca. -8 degrees C in frozen [NO3-] > 200 microM samples warmed at H = 0.70 degrees C min(-1) under continuous irradiation, and also in the dark from samples that had been photolyzed at -30 degrees C. The amounts of NO2 released in individual thermograms, SigmaN, increase less than linearly with [NO3-] or the duration of experiments, revealing the significant loss of photogenerated NO2. The actual SigmaN proportional, variant [NO3-]1/2 dependence (at constant H) is consistent with NO2 hydrolysis: 2NO2 + H2O --> NO3- + NO2- + 2H+, overtaking NO2 desorption, even below the eutectic point (-18 degrees C for aqueous NaNO3). The increasingly larger NO2 losses detected in longer experiments (at constant [NO3-]) are ascribed to secondary photolysis of trapped NO2. The relevance of present results to the interpretation of polar NO2 measurements is briefly analyzed.

Characterization of Silicate Complexes in Aqueous Sodium Sulfate Solutions by FAB-MS

When the sodium ion (Na+) concentration is increased above 0.5 mol-dm−3 (M), the concentrations of dissolved silica in aqueous sodium chloride (NaCl) and sodium nitrate (NaNO3) solutions decrease because of the salting out effect. On the other hand, the concentration of the dissolved silica in aqueous sodium sulfate (Na2SO4) solutions increases monotonously as the concentration of Na+ is increased above 0.5 M. The purpose of this study is to determine the reasons why the salting-out effect is not observed in Na2SO4 solutions. FAB-MS (Fast Atom Bombardment Mass Spectrometry) was used to sample directly the silica species dissolved in aqueous Na2SO4, NaCl, and NaNO3 solutions. In the FAB-MS spectra of these solutions, the peak intensity ratios of the linear tetramer to the cyclic tetramer largely increased for Na+ concentrations between (0.1 and 1) M. This shows that some characteristics of the Na2SO4 solutions are similar to those of the NaCl and NaNO3 solutions. In Na2SO4 solutions, however, when the concentration of Na+ is higher than 1 M, the peak intensity of the dimer is much higher than those of the other silicate complexes. In Na2SO4 solutions, the SO42− ion undergoes partial hydrolysis to form HSO−4 and OH− is produced. In particular, in the range where the concentration of SO42− is high, the pH of the solution increases slightly. This higher pH yields more dimers from the hydrolysis of silicate complexes. This increase in dimer production agrees with the observation that silica dissolves in sodium hydroxide (NaOH) solutions mainly as a dimer when the concentration of NaOH is less than 0.1 M. In Na2SO4 solutions at high concentrations, a salting-out effect is not observed for silica. This is due to the increase in the concentration of OH−, which accelerates the hydrolysis of silica and results in dimer formation.

Densities, Apparent Molar Volumes and Viscosities of Concentrated Aqueous NaNO3 Solutions at Temperatures from 298 to 607 K and at Pressures up to 30 MPa

Densities of four (2.124, 2.953, 5.015 and 6.271 mol-kg−1) and viscosities of eight (0.265, 0.503, 0.665, 1.412, 2.106, 2.977, 5.015 and 6.271 mol-kg−1) NaNO3(aq) solutions have been measured with a constant-volume piezometer immersed in a precision liquid thermostat and using capillary flow techniques, respectively. Measurements were made at pressures up to 30 MPa. The temperature range was 298–607 K for the density measurements and 298–576 K for the viscosity measurements. The total uncertainty of density, viscosity, pressure, temperature and composition measurements were estimated to be less than 0.06%, 1.6%, 0.05%, 15 mK and 0.02%, respectively. The temperature, pressure and concentration dependence of density and viscosity of NaNO3(aq) solutions were studied. The measured values of density and viscosity of NaNO3(aq) were compared with data and correlations reported in the literature. Apparent molar volumes were derived using the measured density values. The viscosity data have been interpreted in terms of the extended Jones–Dole equation for strong electrolytes. The values of the viscosity A-, B-, D- and F-coefficients of the extended Jones–Dole equation for the relative viscosity (η/η0) of NaNO3(aq) solutions were evaluated as a function of temperature. The derived values of the viscosity A- and B-coefficients were compared with the results predicted by Falkenhagen–Dole theory of electrolyte solutions and calculated with the ionic B-coefficient data.

Synthesis, Branched Structure, and Solution Property of Hyperbranched d-Glucan and d-Galactan

The ring-opening multibranching polymerizations of 1,6-anhydro-β-d-glucopyranose (1) and 1,6-anhydro-β-d-galactopyranose (2) have been studied in order to synthesize hyperbranched polysaccharides. The solution polymerization in propylene carbonate and the bulk polymerization of 1 and 2 using a thermally induced cationic initiator proceeded through a ring-opening reaction and a proton transfer reaction to afford highly water-soluble polysaccharides, i.e., poly-1 and poly-2, respectively. For the polymers from 1 and 2 with the same polymerization conditions, the Mw,SLS and yield of poly-1 were higher than those of poly-2. Here, poly-1 and poly-2 were characterized as hyperbranched polysaccharides consisting of α- and β-linked d-hexopyranosyl and d-hexofuranosyl repeating units, hyperbranched d-glucan and d-galactan, respectively. In addition, poly-1 and poly-2 had ca. 30−40 mol % nonreducing d-hexopyranosyl and d-hexofuranosyl terminal units, and the degree of branching was ca. 0.38 for poly-1 and 0.44−0.60 for poly-2. The respective viscosities of poly-1 and poly-2 in aqueous NaNO3(0.2 mol·L-1) solution were very low with the intrinsic viscosity values of 0.023−0.042 dL·g-1. The steady shear flow of poly-1 in aqueous solution exhibited a Newtonian behavior with steady shear viscosities independent of the shear rate, even at high concentrations. The results indicated that the characteristics of the viscosities were attributed to the spherical structure of the hyperbranched polysaccharide in aqueous solution.

ＴＷ法によるネフェリンの合成

Nepheline was synthesized by the TW method. As the starting solution, each aqueous solution of NaNO3 and Al(NO3)39H2O was dissolved in proper amount of distilled water. The constant quantity of Si(OC2H5)4(TEOS) and a small amount of 2M-HCl as catalysis were mixed into the starting solution. A part of NaNO3 was also replaced by KNO3. Nepheline began to form at a certain temperature near 800°C. It was thought that nepheline was produced by a phase transformation of the low-carnegieite under the condition of decreasing of its component. It was also thought that nepheline may be formed by phase transformation of the low-carnegieite in preference to the formation of high-carnegieite through its modification at a certain temperature between 800°C and 900°C, and at a given composition with KNO3 of 15 mole%. In a sample obtained by heating the gel No.7 prepared by replacing the part of NaNO3 of 4.49 × 10-2 mole with KNO3 of 1.35 × 10-2 mole at 1100°C for 30 min, the pure nepheline in a single phase was obtained.

Existence of two forms of nitrate ion in dilute aqueous solutions. Thermodynamic parameters of interconversion

Two well-defined isosbestic points (at 265 and 313 nm) were found in the UV absorption spectra of dilute (0.06 mol dm−3) aqueous solutions of NaNO3, KNO3 and (NMe4)NO3, measured at 13 temperatures in the (10–70) °C range. This finding, together with the apparent cation-independence of the spectra (confirmed by several statistical tests) indicates the existence of a chemical equilibrium between two species differing in the structure of solvation shells: α-NO3− ⇌ β-NO3−. Assuming the constancy of standard conversion enthalpy, ΔrH°, in the experimental temperature range, a simple nonlinear programming algorithm, maximizing the linearity of the ln K° vs. 1/T relationship, was devised in order to compute optimized estimates of K° (T), ΔrH° and ΔrS°, as well as the individual spectra of α-NO3− and β-NO3− species. The following results were obtained: K° ranges from ≈0.08 (10 °C) to ≈0.25 (70 °C), ΔrH° = 15 kJ mol−1, ΔrS° = 31 J K−1 mol−1, λmax(α-NO3−) = 301 nm, emax(α-NO3−) = 7.8 cm2 mmol−1, λmax(β-NO3−) = 317 nm, emax(β-NO3−) = 5.7 cm2 mmol−1. Since the ΔrH° value falls inside the range of the energies of hydrogen-bond breaking and, in addition, ΔrS° > 0, it is hypothesized that the α → β conversion might include the rupture of one hydrogen bond (in the hydration shell) per one α-NO3− entity.

Densities and Apparent Molar Volumes of Aqueous NaNO3 Solutions at Temperatures from 292 to 573 K and at Pressures Up to 30 MPa

Densities of four aqueous NaNO3 solutions (0.100, 0.303, 0.580, 0.892 mol-kg−1 H2O) have been measured in the liquid phase with a constant-volume piezometer immersed in a precision liquid thermostat. Measurements were made at ten isotherms between 292 and 573 K. The range of pressure was 0.1–30 MPa. The total uncertainty of density, pressure, temperature, and concentration measurements were estimated to be less than 0.06%, 0.05%, 10 mK, and 0.014%, respectively. Values of saturated densities were determined by extrapolating experimental P-ρ data to the vapor pressure at fixed temperature and composition. Apparent molar volumes were derived using measured values of density for the solutions and for pure water. The apparent molar volumes were extrapolated to zero concentration to yield partial molar volumes at infinite dilution. The temperature, pressure, and concentration dependence of partial and apparent molar volumes were studied. The measured values of density and apparent and partial molar volume were compared with data reported in the literature.

MEASUREMENT OF CONDUCTIVITY OF SULPHIDE PARTICLES DISPERSED IN WATER

A method for measuring the electrical conductivity of particles dispersed in water is tested on common sulphide mineral samples (chalcocite, chalcopyrite, galena, pyrite and sphalerite). Using an automated conductivity settling technique, aqueous solutions of KCl and NaNO3 were used to change the conductivity of the medium. The particle conductivity was estimated at the iso-conductivity point where the solution and the particles have the same conductivity. The adsorption of xanthate significantly reduced the conductivity of chalcopyrite and copper activation increased the conductivity of sphalerite but not lead activation. These observations suggest that the measured conductivity is associated with the solid/water interface. The conductivity values are compared with electrochemical rest potential values from literature.Une méthode de mesure de la conductivité électrique de particules dispersées dans de l’eau est évaluée avec des échantillons de minéral de sulfure commun (chalcosine, pyrite cuivreuse, galène, pyrite et fausse galène.) Utilisant une technique automatisée de sédimentation par conductivité, on a utilisé des solutions aqueuses de KCl et de NaNO3 pour changer la conductivité du milieu. On a estimé la conductivité de la particule au point d’iso-conductivité où la solution et les particules ont la même conductivité. L’adsorption du xanthate réduisait significativement la conductivité de la pyrite cuivreuse et l’activation du cuivre augmentait la conductivité de la fausse galène, mais pas l’activation du plomb. Ces observations suggèrent que la conductivité mesurée est associée avec l’interface solide/eau. On compare les valeurs de conductivité avec les valeurs de la littérature du potentiel électrochimique au repos.

LURGI WINS CONTRACT FOR METHANOL PLANT

In aqueous solution, both nitrate and nitrite are planar, monovalent, and have the same elements but different sizes and charge densities. Comparing the viscosity of NaNO2 and NaNO3 aqueous solutions provides an opportunity to determine the relative importance of anion size versus strength of anion interaction with water. The viscosity of aqueous NaNO2 and NaNO3 were measured over a temperature and concentration range relevant to nuclear waste processing. The viscosity of NaNO2 solutions was consistently larger than NaNO3 under all conditions, even though nitrate is larger than nitrite. This was interpreted in terms of quantum mechanical charge field molecular dynamics calculations that indicate that nitrite forms more and stronger hydrogen bonds with water per oxygen atom than nitrate. These hydrogen bonds inhibit rotational motion required for fluid flow, thus increasing the nitrite solution viscosity relative to that of an equivalent nitrate solution.

Dependence on Ionic Strength of the Hydrolysis Constants for Dioxouranium(VI) in NaCl(aq) and NaNO3(aq), at pH &lt; 6 and t = 25 °C

The hydrolysis of UO22+ was studied potentiometrically (H+−glass electrode) in NaCl (0.1−4.5 mol L-1) and NaNO3 (0.1−1 mol L-1) aqueous solution, at pH < 6 and t = 25 °C. Computer calculations indi...

Competitive transport of toxic metal ions by polymer inclusion membranes

The paper gives a short overview of application of polymer inclusion membranes (PIMs) for separation and removal of metal ions. Investigation of the selective removal of toxic metal ions, i.e. Cr(VI), Cd(II), Zn(II) from acidic chloride aqueous solutions, as well as trace radionuclides, i.e., 137Cs, 90Sr and 60Co from wastewaters using transport across polymer inclusion membranes was studied. The carriers, i.e., tri-n-octylamine for anionic metal species, as well as dibenzo-21-crown-7, tertbutyl-dibenzo-21-crown-7, and dinonylnaphtalenesulfonic acid for metal cations were incorporated into polymer inclusion membranes composed of cellulose triacetate as a support and o-nitrophenyl pentyl ether as a plasticizer. Selective transport of chromium(VI) over zinc(II) and cadmium(II) chloride complexes through PIMs was observed. Competitive transport of trace radionuclide ions, i.e., 137Cs, 90Sr, and 60Co from NaNO3 aqueous solutions across polymer inclusion membranes containing a mixture of dinonylnaphtalenesulfonic acid, and dibenzo-21-crown-7 as the carrier provide the selectivity order Cs(I)>Sr(II)>Co(II).

Superabsorbent polymeric materials IX: Effect of cationic structure on swelling behavior of crosslinked poly(sodium acrylate‐co‐cationic monomers) in aqueous salt solutions

Two series of xerogels based on sodium acrylate (SA), trimethyl methacrylamidopropyl ammonium iodide (TMMAAI), trimethyl methacryloyloxyethyl ammonium iodide (TMMAI), and N,N′-methylene-bis-acrylamide (NMBA) as a crosslinker were prepared by inverse suspension polymerization. The water absorbency and swelling kinetic behavior for these xerogels in water or various saline solutions were investigated. The results showed that the swelling behaviors of these absorbents are related to their chemical structures, their compositions, and the type of external salt solutions. There would be effective improvement in the water absorbency of these two gel series by copolymerizing SA with a small amount of cationic monomer (TMMAAI or TMMAI). The initial absorption rates in deionized water were found to be faster for TM series gels than for TA series gels. The two series of superabsorbents had a tendency to absorb water in dilute nitrate aqueous solutions in the order: Fe3+, Ni2+, Ca2+, Cu2+, and Na+ for Fe(NO3)3, Ni(NO3)2, Ca(NO3)2, Cu(NO3)2, and NaNO3 aqueous solution, respectively. The absorbency and initial absorption rate for these gels were related to the gel compositions and salt concentrations. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1827–1837, 2001

Superabsorbent polymeric materials IX: Effect of cationic structure on swelling behavior of crosslinked poly(sodium acrylate‐co‐cationic monomers) in aqueous salt solutions

AbstractTwo series of xerogels based on sodium acrylate (SA), trimethyl methacrylamidopropyl ammonium iodide (TMMAAI), trimethyl methacryloyloxyethyl ammonium iodide (TMMAI), and N,N′‐methylene‐bis‐acrylamide (NMBA) as a crosslinker were prepared by inverse suspension polymerization. The water absorbency and swelling kinetic behavior for these xerogels in water or various saline solutions were investigated. The results showed that the swelling behaviors of these absorbents are related to their chemical structures, their compositions, and the type of external salt solutions. There would be effective improvement in the water absorbency of these two gel series by copolymerizing SA with a small amount of cationic monomer (TMMAAI or TMMAI). The initial absorption rates in deionized water were found to be faster for TM series gels than for TA series gels. The two series of superabsorbents had a tendency to absorb water in dilute nitrate aqueous solutions in the order: Fe3+, Ni2+, Ca2+, Cu2+, and Na+ for Fe(NO3)3, Ni(NO3)2, Ca(NO3)2, Cu(NO3)2, and NaNO3 aqueous solution, respectively. The absorbency and initial absorption rate for these gels were related to the gel compositions and salt concentrations. © 2001 John Wiley &amp; Sons, Inc. J Appl Polym Sci 81: 1827–1837, 2001